Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$31.64	5.552%	$33.3967	$33.40	$33.40	$33.40
Purchase #2	$71.72	13.113%	$81.1246	$81.12	$81.10	$81.10
Purchase #3	$188.49	5.819%	$199.4582	$199.46	$199.45	$199.50
Purchase #4	$237.89	11.462%	$265.157	$265.16	$265.15	$265.20
Purchase #5	$165.42	10.302%	$182.4616	$182.46	$182.45	$182.50
Purchase #6	$247.27	4.753%	$259.0227	$259.02	$259.00	$259.00
Purchase #7	$92.29	8.442%	$100.0811	$100.08	$100.10	$100.10
7 purchase totals =	$1,034.72		$1,120.7019	$1,120.70	$1,120.65	$1,120.80